X-ray positioner with side-mounted, independently articulated arms

ABSTRACT

Two independently articulated arms, each having at least two independent axes of motion, support an X-ray tube and X-ray detector, respectively, are mounted offset to the patient and controlled to simulate a wide variety of conventional X-ray positioners. The two arms are each supported at one end by a common base wherein the common base provides at least one common axis of motion for both the first and second articulated arms. Further, an axis controller sends movement signals to the common axis and independent axes and receives position signals from the common axis and independent axes to coordinate movement of the first and second arms according to a predefined program.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/334,745 and entitled “X-RAY POSITIONER WITHSIDE-MOUNTED, INDEPENDENTLY ARTICULATED ARMS” filed on Nov. 15, 2001,the disclosure of which is hereby incorporated by reference as if setforth in its entirety herein.

BACKGROUND OF INVENTION

This application relates to medical x-ray positioners and in particularto a positioner using independently articulated arms to support thex-ray source and x-ray detector.

Conventional x-ray positioners provide mechanical supports to hold anx-ray source and x-ray detector in opposition about a patient for alimited number of specific procedures. For procedures in which thepatient is standing, the x-ray source may be attached to a pillarallowing adjustment in its height as directed toward an x-ray detectorattached to an opposing wall or a second similar pillar. For proceduresin which the patient is supine, the x-ray source and detector may beattached to opposite sides of a patient table. Alternatively the x-raysource and the detector may be attached to opposite ends of a C-armwhich is supported by a sliding collar allowing the angle of the x-raysthrough the patient to be varied.

Multi-axis robotic arms, positioned above and below the patient table,have been proposed to provide support for the x-ray source and x-raydetector such as may reduce interference between the support structureand other equipment and personnel. See, for example, U.S. Pat. No.6,200,024 to Negrelli citing U.S. Pat. No. 4,894,855 to Kresse.

Such systems require complex multi-axis movement for simple adjustmentsof the x-ray tube and detector in angulation or translation, and appearto have limited utility for certain common x-ray procedures such asthose requiring the patient to stand. Further such systems make itdifficult or impossible to swap the location of the x-ray source frombeneath the patient to above the patient, when the patient is supine,and an improved image might thereby be obtained.

SUMMARY OF INVENTION

The present invention provides a simplified mechanism for independentlysupporting an x-ray tube and detector for greater positioningflexibility yet providing simplified axis motion for typicalrepositioning actions. Generally the invention provides twoindependently articulated arms holding the x-ray tube and detector,respectively, where both arms mounted to a common supporting surfaceoffset to one side of the patient. The arms present a fully variableC-shaped structure, avoiding the invariable bulk of a fixed C-arm, whilestill providing a simple and intuitive structure for holding the x-raytube and x-ray detector in opposition. The offset mounting of the armsprovides a greater range of positioning than may be obtained when thearms are mounted above and below a patient table. Mounting the arms on acommon side of the patient reduces the number of axes required forflexible repositioning, allowing some axes to be implemented in commonto reduce the systems mechanical complexity and improve performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of one embodiment of the positioner of thepresent invention showing offset mounting of two independentlyarticulated arms holding an x-ray source and x-ray detector assembly,respectively;

FIG. 2 is a perspective view of the detector of FIG. 1 showing a tiltingupward of an integral display of the detector assembly and axes ofmovement of a control handle supported by the detector assembly;

FIG. 3 is a cross-sectional view of the detector assembly of FIG. 2taken along lines 3—3 of FIG. 2 showing the normal registration of anx-ray detector and the display;

FIG. 4 is a view (top or side) of the articulated arms of the FIG. 1showing, in phantom, arm movement implementing an increasedsource-to-detector distance;

FIG. 5 is a side elevational viewing of the articulated arms of FIG. 1showing positioning of the arms for lateral imaging;

FIG. 6 is an exploded perspective diagram showing various options foradding common axes to the articulated arms of FIG. 1 for differentprocedures;

FIG. 7 is a schematic block diagram of the servo motors associated withthe axis of FIGS. 1 and 6 and a controller for controlling the axes aswell as the x-ray detector and x-ray source according to the presentinvention;

FIG. 8 is a functional diagram of tasks implemented by the controller ofFIG. 7 to control the axes according to one embodiment of the invention;

FIG. 9 is a functional diagram task implemented by the controller ofFIG. 7 to automatically or semi-automatically track a bolus according toone embodiment of the invention;

FIG. 10 is a front elevational view of a supine patient showing thex-ray detector and x-ray source positioned by the present invention inthe offset opposition; and

FIG. 11 is a perspective view of the x-ray detector and x-ray source ofFIG. 10 showing offset collimation of the x-ray source and a region ofinterest display shown on the display x-ray detector assembly.

DETAILED DESCRIPTION

Referring now to FIG. 1, a multi-mode x-ray positioner 10 per thepresent invention provides an x-ray source 12 and an x-ray detector 14.The x-ray source 12 generally includes an x-ray tube, the necessarycooling components, collimators, and shielding as will be understood tothose of ordinary skill in the art. The x-ray detector 14 may be alightweight flat panel detector such as may be fabricated as an array ofdetectors, an amorphous silicon detector panel or other imaging device.The x-ray detector is part of a detector assembly 16 to be described ingreater detail below.

The x-ray source 12 directs an x-ray beam generally along a central ray13 whereas the x-ray detector 14 receives x-rays generally along acentral ray 15 normal to the surface thereof. A patient 50 may besupported supine on a table 56 so as to be aligned with the central rays13 and 15. For this purpose, the table 56 is composed of aradiotranslucent material of a type well known in the art.

Referring also to FIG. 4, each of the x-ray source 12 and the x-raydetector 14 are held, respectively, on separate articulated robot arms18 and 20. The arms 18 and 20 are attached at a first end to a base 22,the latter preferably supported against a vertical surface with the armsextending laterally therefrom.

The arms 18 and 20 attach to the base 22 at shoulder axes 26 and 24,respectively. Each shoulder axes 26 and 24 provides angulation of itsrespective arm 18 or 20 about parallel axes extending generally alongthe plane of the base 22, the latter being parallel to a vertical planedefining the surface to which the base 22 is attached. Generally theterm “axis” henceforth will refer both to a mechanical joint and themathematical vector describing movement of that joint. The particularmeaning will be evident from context.

Attached to and extending from shoulder axes 24 and 26 are upper arms 30and 32, respectively, which terminate in elbow axes 34 and 36,respectively, each also providing for angulation along parallel axesalso parallel to axes 24 and 26. Forearms 38 and 40 extend from elbowaxes 34 and 36, respectively, and the latter which provide telescopingextension axes 42 and 44 permitting translation movement of wrist axes46 and 48 along the length of the forearms 38 and 40.

Wrist axes 46 and 48 provide angulation about parallel axes alsoparallel to axes 24 and 26 and connect, respectively, to the x-raydetector assembly 16 and x-ray source 12. It is to be understood thatthe x-ray source and x-ray detector assembly are not limited to mountingon a particular arm and may be replaced by other devices to meet otherclinical needs.

It will be understood from this description that each of the arms hasfour axes of motion comprised of shoulder axes 24, elbow axis 34 andwrist axis 46 and extension axis 42, for arm 20 and shoulder axes 26,elbow axis 36, and wrist axis 48, and extension axis 44 for arm 18.Generally, motion of shoulder axes 24 and 26 control the angle of upperarms 30 and 32 and the position of elbow axes 34 and 36 with respect toshoulder axes 24 and 26. Likewise, motion of elbow axes 34 and 36control the angle of forearms 38 and 40 and the position of wrist axes46 and 48 with respect to the elbow axes 34 and 36. Motion of extensionaxes 42 and 44 control the separation of elbow axis 34 and wrist axis 46and elbow axis 36 and wrist axis 48, respectively, and motion of wristaxes 46 and 48 control the angle of detector 14 and x-ray source 12.

Each of axes 24, 26, 34, 36, 42, 44, 46, and 48 are enabled for servocontrol meaning that they may be moved electronically in response to aposition signal received from the axis so that precise positioningand/or velocity control of each axis may be had through a centralprocessor as will be described below.

Referring again to FIGS. 1 and 4, the arms 18 and 20 may be maneuveredto position the x-ray source 12 and detector assembly 16 in alignment onopposite sides of a patient 50 at a first source-to-detector distance52. Subsequently, the arms 20 may be maneuvered, through a combinedmotion of their axes, to provide a source-to-detector distance 54substantially greater than source-to-detector distance 52, whilemaintaining alignment. Such separation is accomplished principally by acombined angulation and extension of the axes 24, 26, 34, 36, 42, 44,46, and 48 and notably does not require an axis of translation alignedwith the central rays 13 and 15 of the source and detector as is typicalof conventional x-ray positioners.

Referring again to FIGS. 1 and 4, the base 22 may be mounted on a waistaxis 64 providing rotation about a line that is horizontal andperpendicular 60 to the plane of the base 22, the rotation as indicatedby arrow 62. Thus, the arms 18 and 20 in their varioussource-to-detector separations 52 and 54 shown in FIG. 4 may be opposedabout a substantially vertical axis (as depicted in FIG. 1) or about ahorizontal axis. The horizontal axis is useful for procedures such aschest x-rays or other situations where the patient is best imaged whilestanding or seated. In these cases, the table 56 would be moved to avertical configuration or moved out of the way altogether. The rotationof the base 22 about the waist axis 64, as with the other axes, is underservo control and provides single axis cranial-caudal angularadjustment.

Alternatively as shown in FIG. 5, the arms 18 and 20 may be manipulatedto provide central rays 13 and 15 perpendicular to the plane of the base22. In this case, the arms 18 and 20 are not deployed symmetrically butelbow axis 34 is moved to an acute position whereas elbow axis 36 ismoved to an obtuse position with extension axis 44 fully extended andextension axis 42 fully retracted. This degree of flexibility isaccomplished because each of the axes 24, 26, 34, 36, 44, 42, 46 and 48are independently controllable.

Referring to FIG. 6, the base 22 may be mounted directly on a wall orthe like by means of stationary collar 70 receiving the waist axis 64.Alternatively, and as also shown in FIG. 1, the base 22 may be attachedto a vertically translating collar 72 also receiving the waist axis 64but providing for vertical translation along tracks 74 also under servocontrol to form translation axis 81. Opposed ends 76 of the track 74 maybe held against the wall or vertical surface by stationary collars 78(only one of which is shown for clarity) similar to stationary collar70. The translation axis 81 allows single axis elevation of the x-raysource 12 and x-ray detector 16.

Alternatively, the end 76 may be received by horizontally translatingcollars 80 moving horizontally along tracks 82 so as to provide ahorizontal servo control translation axis 85 for the tracks 74, the base22, and thus the arms 18 and 20.

In an alternative configuration, the base 22 may be mounted tohorizontally translating collar 90 of the tracks 92 positioned to extendhorizontally along axis 91. The ends 94 of the tracks 92 may be attachedeither to a stationary collar 96, similar to stationary collars 78 or tohorizontally vertically collars 98 but with the track 100 positioned tomove along vertical axis 83, the latter having its ends 102 fixed to astationary surface such as a wall or the like. The translation axis 91allows single axis horizontal repositioning of the x-ray source 12 andx-ray detector 16.

While the two configurations represented in tree fashion by the branchesending with the axis 85 and 83 of FIG. 6 result in the same degrees offreedom, they provide alternate evolution paths allowing the positioner10 to be upgraded from a base system having only base 22 and arms 18 and20 to a full featured system through the addition, respectively, ofvarious components of vertically translating collar 72, or horizontallytranslating collars 90. A wiring harness system (not shown) allows eachof these axes to be added to an axis controller to provide improvedfunctionality as will be described below.

Referring now to FIGS. 1, 2 and 3, the detector assembly 16 includes aflat panel x-ray detector 14 on a first surface normally facing thex-ray source 12 and held within a supporting frame 106. The flat panelx-ray detector 14 is sized to receive a collimated beam of x-rays 104from the x-ray source 12 and positioned immediately behind the flatpanel x-ray detector 14 is a blocking lead shield 110. This may befollowed by processing circuit cards 112 and 114. Following the circuitcards 112 and 114 is a flat panel display 116.

The flat panel display 116 may receive an image registered with theimage received by the x-ray detector 14 for display to a human operatorviewing the image from the top side of the detector assembly 16. In thisconfiguration, the image displayed by the flat panel display 116 remainsin perfect registration with the x-ray detector 14 thus eliminatingconfusion that can result in normal fluoroscopy systems where the imagemay rotate on a stationary monitor with respect to the patient as thepositioner is moved. As shown in FIG. 2, in order to provide for obliqueviewing angles, the flat panel display 116 may hinge upward about one oftwo perpendicular hinge axes 128 or 130 so as to provide better viewingfor the user while still maintaining rotational registration with thepatient's anatomy.

Also supported on the top side of the frame 106 is a touch screen panel118 providing for basic level control of the x-ray system includingx-ray tube voltage, exposure time, and other techniques. The frontportion of the frame 106 also supports a multi-axis control handle 120providing a number of signals depending on movement of the handle by theoperator either vertically, horizontally or in rotation as shown byarrows 124 and shown also in FIG. 2. A second blocking lead shield 108may be attached to a portion of the supporting frame 106 positionedtoward the operator during normal use as shown in FIG. 1.

The circuit cards 112 provide a multiplexed signal collecting the datafrom the x-ray detector 12 for a central controller to be described. Thecircuit card 114 provides an interface for the central controller withthe touch screen panel 118 and a multi-axis control handle 120.

Referring now to FIG. 7, each of the different axes 24, 26, 34, 36, 42,44, 46, 48, 64, 81, and 84 provides feedback signals and receives acommand signals from an axis control interface 132 so as to provide forservo control of each axis according to techniques well known in theart. The axis control interface 132 connects to a central bus 134 of thecentral controller 136. The central controller 136 is constructedaccording to conventional computer architecture and includes a processor138 communicating with the bus 134 and with memory 140 which may includeboth random access and magnetic disk memory or other mass storagedevices. A modem 142 also communicating with the bus provides a path fordownloading of information and programs into the memory 140 as will bedescribed.

The controller 136 also provides a signal through port interface 144(also attached to bus 134) to a high voltage power supply 146 feedingthe x-ray source 12 so as to provide control over current and x-ray tubevoltage and on and off duty cycle. Diagnostic signals may also bereceived from the power supply 146 via this port interface. Additionalports interfaces 150, 152, and 154 provide communication between thecentral bus 134 and the control handle 120, the x-ray detector 14, theflat panel display 116, and the touch screen panel 118 described above.

During operation, the processor 138 runs a control program 170 held inmemory 140 to control the various axes 24, 26, 34, 36, 42, 44, 46, 48,64, 81, and 84 and to control the x-ray exposure of a patient and toreceive and process the image data for display on the flat panel display116 according to commands received through the control handle 120 andtouch screen panel 118.

The memory 140 may also hold a hardware configuration file 160 and oneor more personality files 162. The hardware configuration file 160stores data on the various components as shown in FIG. 6 that have beenassembled together to produce the particular positioner 10. Thepersonality files 162 contain models for how the x-ray system willoperate, for example, emulating a fluoroscopy, spot film device or C-armtype configuration. Each of the personality files 162 includes a zeroconfiguration variable describing how the positioner 10 should beinitialized prior to patient scan. More generally, the personality files162 may include one or more predefined procedures involving dynamicmovement of the arms 18 and 20 for a particular procedure such astomography. The personality files 162 also define how the control handle120 will be interpreted to axes movement.

For example, it may be desired to operate the positioner to emulate afluoroscopy machine with a C-arm type structure. In this case,fluoroscopy C-arm type personality files 162 would be loaded and invokedthrough touch screen panel 118.

Referring now to FIG. 8, the control program 170 makes use of theconfiguration file 160 and the personality files 162 to implementcontrol function blocks for the operation of the positioner 10. A firstfunction block provides a control map 172 mapping movements of thecontrol handle 120 to movements in a room coordinate system. Forexample, if the positioner 10 is programmed to emulate a C-arm typedevice, rotation of the control handle 120 may cause angulation of theC-arm effectively rotating the central rays 13 and 15 about a centerpoint 174 shown in FIG. 7. The center point may be defined by the centerof the base 22 or be arbitrarily located through multiple axis motion asdetermined by the personality file 162. Vertical and horizontal movementof the control handle 120 may raise or move laterally the virtual C-armsimultaneously moving the x-ray source 12 and x-ray detector 14 as ifthey were connected by a rigid bar. The assignment of the control handle120 to particular room coordinates is arbitrary and even in this case,for example, they may be assigned differently with vertical movement ofthe control handle 120 changing source-to-detector distance rather thanraising or lowering the x-ray detector 14 and x-ray source 12 in unison.Likewise, the motion of the positioner components with respect to eachother may be arbitrarily defined to simulate positioners of varyinggeometries.

The control map 172 produces commands 178 in room coordinates or virtualmachine coordinates (the latter which describe motion of machinecomponents, such as a C-arm which do not in fact exist). The commands178 are received by axis parsing and translation module 180 whichinterrogates the hardware configuration file 160 to see what axes areavailable in order to realize the coordinate commands 178. Generallythere will be more than one combination of different axes movements andthe axis parsing and translation module 180 will select among theselooking at other considerations, for example, accessibility and theavoidance of collision within the patient space.

The axis parsing and translation module 180 translates the commands 178into positioner axes commands 182 which are provided to one of the arms,preferably 20. The second arm 18 will receive positioner axiscoordinates 184 from a virtual axis link 186. The virtual axis link 186receiving as inputs the positioner axes commands 182 from the axisparsing and translation module 180 and providing correspondingpositioner axis commands 184 to achieve the desired virtual linkagebetween the x-ray source 12 and x-ray detector 14 as defined by theconfiguration file 160 and the personality files 162. Generally thislinkage will amount to simulation of a virtual structure directlyconnecting the x-ray source 12 and x-ray detector 14 together such as abar or C-arm or the like.

Because the arms 18 and 20 are not so connected, a variety of otherpersonalities may be adopted including those which provide for complexindependent movement of the x-ray source 12 and x-ray detector 14 fortomography and the like.

As mentioned, a zero configuration variable may be read by the controlprogram 170 to determined the starting position of the positioner 10,e.g., whether the x-ray source 12 and x-ray detector 14 are positionedhorizontally with respect to each other or laterally or for a standingpatient or the like. Zero configuration task 190 handles thisinitialization of the axes making use of the hardware configuration file160 and the particular machine model in personality files 162. Theprogram 170 may also implement a procedure engine 192 which recordsparticular procedures including techniques, exposure times, motion andpositioning of the arms that may be collected and exchanged byphysicians or skilled practitioners. These procedures may be invokedthrough the touch screen panel 118.

Referring momentarily to FIG. 7, the hardware configuration file 160 andthe various personality files 162 may be loaded via the modem 142 andthus the positioner 10 may be configured remotely and users of thepositioner 10 may trade different configurations, personality modulesand procedures with each other as they are developed.

Referring now to FIG. 9, one such procedure may receive image data fromthe x-ray detector 14 into a summing unit 193 implemented by the program170 and also into an image buffer 194. A subtraction of a previouslybuffered image and the current image yields motion data 195 which may beoperated on by a morphometric filter 196 to identify, for example, amoving bolus of contrast medium in certain types of studies. Themorphometric filter may be initialized by user parameters 202 that maybe part of a procedure engine module being one of personality files 162.

The location of the bolus relative to the position of the x-ray detector14 may be extracted as position coordinates 200 in the room or machineframe of reference. The position coordinates 200 may be fed directly tothe control map 172 so as to provide for automatic bolus tracking inwhich the arms 18 and 20 are automatically moved so as to maintain abolus of contrast medium within the x-ray beam. Memory 140 may alsostore images including video sequences and the like, user parameter dataand other data well known in the art.

Referring now to FIG. 10, the small profile of the detector assembly 16allows for more flexible positioning with respect to patient 50 thanwould be obtained with a comparable apertured image intensifier 210shown in dotted outline. This flexibility is enhanced by the ability tooffset the central ray 13 of the x-ray source 12 with respect to theaxis 15 of the x-ray detector 14 by displacement of the x-ray source orby offset collimation of the x-ray beam. In either case, when a smallbeam of x-rays is required, that beam may be directed to a desired areaof the x-ray detector 14 rather than to the center of the x-ray detector14 and that area preferentially scanned. This capability allows improvedpositioning with respect to the patient 50 without obstruction by theedges of the detector assembly 16 for large apertured x-ray detectors 14such as may be desirable in other situations.

Referring to FIG. 11, as mentioned, the displacement of the central ray13 may be performed by angulation of the x-ray source 12 throughadditional axes (not shown) or by adjustment of a collimator 212 tocollimate the x-ray beam to less than the area of the detector but alsoto offset the center of the beam toward a detector edge. Control of acollimator 212 to control the exit aperture of the x-ray beam is wellknown in the art, and is modified only to displace the central ray 13 ofthe beam. Positioning of the detector assembly 16 may be enhanced by thegeneration of an x-ray reception pattern 214 on the face of the flatpanel display 116, showing the operator the active area of the x-raydetector 14 on the opposite side of the detector assembly 16 prior toexposure.

It is specifically intended that the present invention not be limited tothe embodiments and illustrations contained herein, but that modifiedforms of those embodiments including portions of the embodiments andcombinations of elements of different embodiments also be included ascome within the scope of the following claims.

What is claimed is:
 1. A multi-operating mode x-ray imaging systemcomprising: an x-ray source producing an x-ray beam directed along asource axis; an x-ray detector detecting x-rays received along adetector axis; a first and second articulated arm each having at leasttwo independent axes of motion, the first articulated arm holding thex-ray source at its first end, the second articulated arm holding thex-ray detector at its first end; a common base supporting second ends ofthe first and second articulated arms providing at least one common axisof motion for both the first and second articulated arms; and an axiscontroller sending movement signals to the common axis and independentaxes and receiving position signals from the common axis and independentaxes to coordinate movement of the first and second arms according to apredefined program.
 2. The multimode x-ray imaging system recited inclaim 1 wherein the common axis of motion is rotation.
 3. The multimodex-ray imaging system recited in claim 1 wherein the common axis ofmotion is translation along a direction selected from the groupconsisting of horizontal direction and vertical direction.
 4. Themultimode x-ray imaging system recited in claim 1 wherein theindependent axes of motion are angulation.
 5. The multimode x-rayimaging system recited in claim 4 wherein the independent axes of motionare parallel.
 6. The multimode x-ray imaging system recited in claim 1where each articulated arm has three independent axes of motion.
 7. Themultimode x-ray imaging system recited in claim 6 wherein one of theindependent axes of motion is translation.
 8. The multimode x-rayimaging system recited in claim 5 wherein the axis of translationeffects a separation between a first axis providing axes of angulationpositioned near the first end of the articulated arm and a second axisproviding an axis of angulation next removed from the first end of thearticulated arm.
 9. The multimode x-ray imaging system recited in claim1 wherein the axis controller coordinates movement of the axes of motionof the articulated arms so as to simulate a rigid arm joining the x-raysource with the x-ray detector during movement of both the x-raydetector and x-ray source.
 10. The multimode x-ray imaging systemrecited in claim 1 wherein the axis controller coordinates movement ofthe axes of motion of the articulated arms so as to hold the axes of thex-ray source and x-ray detector in alignment with movement of the x-raysource and x-ray detector.
 11. The multimode x-ray imaging systemrecited in claim 10 wherein the axis controller coordinates movement ofthe axes of motion of the articulated arms so as to maintain the axes ofthe x-ray source and x-ray detector in alignment with a directionselected form the group consisting of vertical and horizontal duringmotion of the x-ray source.
 12. The multimode x-ray imaging systemrecited in claim 1 wherein the axis controller coordinates movement ofthe independent axes to orbit about a point not intercepted by anyindividual of axes of angular movement of the first and secondarticulated arm.
 13. The multimode x-ray imaging system recited in claim1 wherein the axis controller coordinates movement of the first andsecond arms to change the distance separating the x-ray detector andx-ray source by controlling the angulation of at least two axes ofmotion.
 14. A multi-operating mode x-ray imaging systemic comprising: apatient support; an x-ray source producing an x-ray beam directed alonga source axis; an x-ray detector detecting x-rays received along adetector axis; a first and second articulated arm each having at leasttwo independent axes of motion, the first articulated arm holding thex-ray source at its first end, the second articulated arm holding thex-ray detector at its first end, wherein second ends of the first andsecond arms are positioned on a common side of the patient support; andan axis controller sending movement signals to the common side andindependent axes and receiving position signals from the common side andindependent axes to coordinate movement of the axes of the first andsecond arms according to a predefined program.
 15. The multimode x-rayimaging system recited in claim 14 wherein the independent axes ofmotion are angulation.
 16. The multimode x-ray imaging system recited inclaim 14 wherein the independent axes of motion are parallel.
 17. Themultimode x-ray imaging system recited in claim 14 where eacharticulated arm has three independent axes of motion.
 18. The multimodex-ray imaging system recited in claim 17 wherein one of the independentaxes of motion is translation.
 19. The multimode x-ray imaging systemrecited in claim 18 wherein the axis of translation effects a separationbetween a first axis providing axes of angulation positioned near thefirst end of the articulated arm and a second axis providing an axis ofangulation next removed from the first end of the articulated arm. 20.The multimode x-ray imaging system recited in claim 14 wherein the axiscontroller coordinates movement of the axes of motion of the articulatedarms so as to simulate a rigid arm joining the x-ray source with thex-ray detector during movement of both the x-ray detector and x-raysource.
 21. The multimode x-ray imaging system recited in claim 14wherein the axis controller coordinates movement of the axes of motionof the articulated arms so as to hold the axes of the x-ray source andx-ray detector in alignment with movement of the x-ray source and x-raydetector.
 22. The multimode x-ray imaging system recited in claim 14wherein the axis controller coordinates movement of the axes of motionof the articulated arms so as to maintain the axes of the x-ray sourceand x-ray detector in alignment with a direction selected from the groupconsisting of vertical and horizontal during motion of the x-ray source.23. The multimode x-ray imaging system recited in claim 14 wherein theaxis controller coordinates movement of the independent axes to orbitabout a point not intercepted by any individual of axes of angularmovement of the first and second articulated arm.
 24. The multimodex-ray imaging system recited in claim 14 wherein the axis controllercoordinates movement of the first and second arms to change the distanceseparating the x-ray detector and x-ray source by controlling theangulation of at least two axes of motion.